Cursor



Patented Jan. 16, 1951 v UNITED :S TATES- PATE NT F Fl C E onasoa.PauLEBoehm, Greenwich, Conn.

I Application October 16, 1947,'Serial'No. 780,132

1 iinverrtion relates to a slide rule :cursor. One of the objects or"invention .is .130 provide arslide rule inursorwhich is simple,practical and flIorough1-y durable Another object of this in- -ventionlisito provide :a :device of the above char- :acter which facilitatesreading and setting and thereby-enhances speed :and :accuracy of :slidemnleiwork. Another obiectioif EthiS invention is to rprovide ia xievice:01 the above character, the "use or which :Will reduce ceye :strain.:Still another (oliiectrofiinventioniis' to provide a deviceof the:above character, rt-he usefulness "of which is motafiedtedbyrscratch-ing and :dirt. -:Sti1l another rohiect (of tthis invention:is zto provide .a :device of the above character which :is :simple :inconstrucrtion and may the economically manufactured. .A .fiurther objectof this invention is to provide 'a idervice :of above rcharacter :whichfacilitates :certaincalculationspnthe :slide rule by eliminating thenecessity of income the slide iior 5110111211 operation. iOther objectswill 'he in :part obvious sand in 'parit pointed 'out hereinafter.

invention accordinglyaconsists in the teaand arrangements of 'parts,all:as will 'he illustradiivly :describedrherem, and theiscopeofLiane-appliication which *will the indicated in the ?following claims.

:Referring :now to the accompanying drawing, in which :are ;s'howntwo ofthe various possible aemhodiments :of this invention,

:E'igure ;1 is .a perspective viewwof the cursor :mnun'ted son a:iportion of a slide rule; Figure 2 is :avertical tsection taken on theline 2-4 of Figure 11;

:E'igure 3:is .aiplan'of:a:modificationiof'the cursor :shown' in Figure:1 i mountedon a 'portion of a slide mule; and Figure'eis'acuentical-sectionzofthe cursor taken on the line -;l'4 :of Figure B.

:Sim'ilar reference characters refer to similar parts throughout "theseveral views 'of the draw- 9mg.

conducive :to a clearer understanding :of :cerifeatures of :thisinvention, it might here be tnointed out vthat most :slide rules areequipped .atcursormade wholly pr in "part .of -'a "transparent material.portion of cursors now "in use'which is rpos'itionedabove the stock andslide zistusualiy aithinshee't or plate of transparentmaterial-whichrhas a .hair line engraved or otherwise provided on thesurface which faces and practically contacts "the graduated faces of thers'hick and slide.

.JEt :hasbeen found thatthis :conventional 'type a cursor is :not.satis'factory tin rma'ny respects.

.6 .Claims. (Cl. 235-70) 'ttures of menstruation, combinations ofelements,

In the :first place the production of a fine hair :line is a-delicateand rather costly manufacturing operation. .Another'difiiculty lies inthe fact that in usesmall particles of dust, dirt, lint and the likeaccumulate in the minute space between the lower surface of the hairline plate of the cursor and the graduated faces of stock and slide..These particles of foreign matter make it sometimes extremely hard toread thescale lines and numbers'and the little groove that makes-thehair line picks up dirt and dust so that the hair line becomessoonblurred and unsuitable for precise readings. .It is accordinglyanother Obie-ct of this invention to-overcome the above-mentioneddifiiculties. 7

Referring now to the drawing; in Figures 1 and 2 a-sirnple slide rule.generally indicated at 9 with only one graduated face is shown. Sliderule 9 includes stock I!) and slide l. The cursongenerally indicatedatl2, covers'only the graduated faces ofstockfll andslide :H. Cursor i2 ismade of one integral piece of transparent material including a mainplate 13 with flange portions Id and -l 5 whichguide the cursor 12 alongthe stock 1 ll by means of the outside grooves It and H isthe stock withwhich the flange portions coact.

The plate I3 is provided with an opening or window 1.8 of rectangularshape. Window 18 has one .edge [9 .locatedapproximately in the center ofthe cursor l2 which extends at right angles to the direction ofmovementof cursor l2 and slide H along stock It. The margin 20 adjacent edgfe J9is very thin and of substantial width. Margin I distortion and thuspermit edge 19 to be correctly set to a numerical value between twoadjacent raduation lines of the "scales oi the slide rule. If edge [9'was'n'ot perpendicular, the distortion cau ed by'view'ing the scalethrough the edge I!) would cause the graduation line on the slide rulenext tothe index edge but underneath margin 21! "to 's'eemto be nearerto the edge thanit really is.

Experiments have further shown that a cur- "sor with a window and indexedge is far superior to 'a 'hairqine cursor. These portions of thescales that'are visible through the window it are seen directly andtherefore in complete clarity because no cloudiness or discoloration ofthe cursor material obstructs the View: "No dust or foreign matter norscratches can accuii-u1ate underneath .the cursor plate where clearvisibility of :greatest importance.

color to make it appear a trifle darker or different from the color orshade of the face of the slide rule 9. This is of definite advantage tothe users eye, as it accents line l9, making it much easier to alignedge It with respect to a certain value on one or more of the scales, orto read the value corresponding to an actual position of the index edgeIt with respect to those scales, In contrast to this, when theconventional hair line is used, the eye is confused by the manygraduation lines on both sides of the hair line. In using the cursordisclosed, the eye has to contend only with the graduation lines to oneside of the index edge I9, namely, the lines visible in the Window I8.

It might here be pointed out that the description hereinabove isillustrative only, and that the invention is not limited to the featuresof the example illustrated and described above. It should also bepointed out that some cursors have more than one hair line, andaccordingly the cursor described above may have more than one window orone or more windows with more than one index or index edge. As anexample of such construction, referring to Figures 3 and a, the width ofthe window 18 may be made so as to equal the logarithmic value of 1r/4:on the A/B scale, and both lateral edges 2|, Zia of the window designedas index edges. Then, by setting the right-hand index edge 2| to X onthe D scale, the area of a circle with diameter X may be read at theleft index edge 2m on the A scale' Thus, a thoroughly efiicient andpractical cursor has been disclosed which is efficient in use andeconomical to manufacture. It will thus be seen that the difficultiesmentioned hereinabove have been successfully overcome and the objectssuccessfully accomplished.

As many possible embodiments may be made of the mechanical features ofthis invention, and as many changes might be made in the embodimentabove set forth, it is to be understood that all matter hereinabove setforth'or shown in the accompanying drawings is to be interpreted asillustrative and not in a limiting sense.

I claim:

1. In a cursor for a slide rule or similar instrument, in combination, aplate member, means mounting said member on said instrument for movementlongitudinally thereof, and means forming an opening in said member,said opening including at least one straight edge extendin transverselyacross the graduated surface of said instrument, the portion of saidmember adjacent said last-mentioned edge being transparent, relativelythin, and of a color different from that of the graduated surface ofsaid instrument.

2. In a cursor for a slide rule or similar instrument, in combination, aplate member, means slidably mounting said member on said instrument formovement longitudinally thereof, the lower surface of said plate memberbeing positioned a minute distance from the graduated surface of saidinstrument, and means forming an opening in said plate member, saidopening having a pair of parallel edges positioned parallel with respectto the graduation lines on said instrument and serving as index edgeswith respect thereto, the portions adjacent said parallel edges being ofsubstantially transparent material, said index edges being spaced fromeach other a distance which represents a predetermined numerical valueat the logarithmic scale existing in at least one of the graduations ofthe Sl de ru iii 3. In a cursor for a slide rule or similar instrument,in combination, a plate member, means slidably mounting said member onsaid instrument for movement longitudinally thereof, the lower surfaceof said plate member being positioned a minute distance from thegraduated surface of said instrument, and means forming an opening insaid plate member, said opening having a pair of paralleledgespositioned parallel with respect to the graduation lines on saidinstrument and serving as index edges with respect thereto, said indexedges being spaced from each other a distance which represents apredetermined numerical value at the logarithmic scale existing in atleast one of the graduations of the sliderule, the portions of saidplate member adjacent said index edges being transparent and ofsubstantially less thickness than said plate, and the faces of saidedges lying in planes extending substantially at right angles to thegraduated surface of said instrument.

4. In a cursor for a slide rule or similar instrument, in combination, aplate member, means slidably mounting said member on said instrument formovement longitudinally thereof, the lower surface of said plate memberbeing positioned a minute distance from the graduated surface of saidinstrument, and means forming an opening in said plate member, saidopening having a pair of parallel edges positioned parallel with respectto thegraduation lines on said instrument and serving as index edgeswith respect thereto, said index edges being spaced from each other adistance which represents a predetermined numerical value at thelogarithmic scale existing in at least one of the graduations of theslide rule, the portions of said plate member adjacent said index edgesbeing relatively thin, transparent, and of a shade or color differentfrom that of the graduated surface of said instrument.

5. Ina slide rule construction of the tvpe wherein there is a stockwhich carries a central slide and which has a flange-receivingguidewayat each edge, said stock and slide having faces in a common plane whichcarry graduation lines which extend transversely of the stock, a unitarycursor slideably mounted on said stock and including a plate portionpositioned on said faces of the stock and slide and a pair of mountingportions extending along the respective edges of the stock and havingflanges which ride in said guideways, said plate portion having anopening therein which xtends transversely of the said faces and whichhas a straight edge along one side which is a parallel to the saidgraduation lines on the stock and slide, said plate member having theportion forming said straight edgeformed of substantially transparentmaterialwhich is relatively thin and has parallel faces, said straightedge having its face in a plane extending substantially at right anglesto the graduated surfaces of the stock. a

6. In a slide rule construction of the type wherein there is a stockwhich carries a central slide and which has a flange-receiving guidewayat each edge, said stock and slide having faces in a common plane whichcarry graduation lines which extend transversely of the stock, a unitarycursor slideably mounted on said stock and including a plate portionpositioned on said faces of the stock and slide and a pair of mountingportions extending along the respective edges of the stock and havingflanges which ride in said guide-- ways, said plate portion having anopening therein which extends transversely of the said faces and whichhas parallel straight edges along the sides 7 2,538,502 5 i 6 which areparallel to the said graduation lines REFERENCES CITED on the stock andslide Said plate member having The following references are of record inthe the portions forming said straight edges formed me of this patent:of substantially transparent material which portions are relatively thinand have parallel faces, 5 UNITED STATES PATENTS said straight edgeshaving their faces in planes Number Name Date extending substantially atright angles to the 277,292 Knight May 8, 1883 graduated surfaces of thestock, said straight 460,930 Cox Oct. 6, 1891 edges being spaced fromeach other a distance 603,695 Keuifel May 10, 1898 which represents apredetermined numerical 10 747,098 Stanley Dec. 15, 1903 value in thelogarithmic scale existing in at least 1,181,672 Keufiel May 2, 1916 oneof said graduations. 2,387,404 Moyer Oct. 23, 1945 PAUL F. BOEHM.2,392,877 Pym Jan. 15, 1946

